What is the difference between 'in' and 'on'?

[Yuty]

English Grammar Tests, Elementary Level

ESL/EFL Test #48 "Common Prepositions", question 8

I like to eat ice cream ......... chocolate sauce on top.

(a) at
(b) with
(c) in
(d) to

English Grammar Tests, Elementary Level

ESL/EFL Test #48 "Common Prepositions", answer 8

I like to eat ice cream with chocolate sauce on top.

Correct answer: (b) with

Your answer was: incorrect
I like to eat ice cream in chocolate sauce on top.
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What is the difference between 'in' and 'on'?

[Mister Micawber]

.
'In' refers to perceived three-dimensional locations (in a box, in a taxi, in a classroom) and 'on' refers to perceived two-dimensional locations (on a table, on a bus, on a street corner).
.
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Native English teacher at Mister Micawber's